1. Field of the Invention
This invention relates to the preparation of methyl-nonyl-acetaldehyde by reacting undecanal and formaldehyde or a compound which forms formaldehyde in the presence of a secondary amine.
2. Discussion of the Prior Art
Methyl-nonyl-acetaldehyde (2-methylundecanal) is a sought-after principal in perfumery because of its strong frangrance of oranges and incense.
A number of processes are known for preparing methyl-nonyl-acetaldehyde. Thus, according to one process, methyl-nonyl-ketone is reacted with ethyl chloroacetate to form the disubstituted glycidic ester, and the ester is then hydrolyzed with sodium hydroxide and, after acidification, converted into the aldehyde by steam distillation. (See Ullmans Enzyklopadie der technischen Chemie, 3rd edition, Vol. 14, page 737).
Another synthesis starts from n-undecanol, which is reacted with methanol in the presence of sodium methylate. 2-methyl-undecanol is formed, which is then dehydrogenated to form the aldehyde. (Chemical Abstracts Vol. 74 [1971], 12552 X.)
The preparation of .alpha.-methylenealdehydes is described in German 16 18 528. Aldehydes of the general formula RCH.sub.2 CHO (where R denotes an alkyl group with 7-10 carbon atoms) are reacted with formaldehyde or substances forming formaldehyde, in the presence of a catalytic amount of ammonia or a primary or secondary amine or salts thereof. The corresponding .alpha.-methylaldehydes, of which .alpha.-methyl-nonyl-acetaldehyde is one example, are then obtained by hydrogenation.
The known methods for obtaining methyl-nonyl-acetaldehyde require the use of pure starting substances that are difficult to obtain. There is, therefore, the problem of providing a process for preparing the aforementioned aldehyde which permits the use of starting substances that are industrially available at low cost.